Stockholders' Equity (Details) (ATM Program [Member], USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
ATM Program [Member]
Stockholders' Equity [Line Items]
Period of agency agreement	3 years
Maximum value of potential common stock available for issue		$ 25,000,000
Percentage sales commission on shares (in hundredths)	3.00%